what does mean "or *skill/spell* ends"

for Example protective bond, there is written :When Protective Bond prevents damage, you lose 6...4 energy or the spell ends. that means, that when you get your energy 0 PB ends?

Yes.

1212121212

Yes, so if you were to weapon swap to a negative energy set, your prot bond would end.

So the key is to have yourself massive regen of energy or dont bother with the skill

ok, thx you guys a lot ^^

That depends on how much energy you have. Negative energy sets offset your total energy in a negative direction. For example, if I go into my negative energy set and have yet to cast a singel spell, I am at 25e.

@OP your assumption was correct.